1. Field of the Invention
This invention relates to a nozzle for use in a fluidized bed mixing/dispersing arrangement mounted in a floor of a fluidized bed reactor for uniformly mixing gaseous, liquid and/or powder reactants and catalysts in the reactor.
2. Prior Art
Fluidized bed reactors are conventionally used in the reaction between hydrocarbons, chlorine source gas, oxygen or air and catalyst powder, which is known as oxychlorination reaction. For the oxychlorination reaction, the fluidized bed reactor is provided in the floor of the fluidized bed with a plurality of mixing/dispersing arrangements each having a nozzle built therein. In some applications, nozzles themselves are used as the mixing/dispersing arrangements. These mixing/dispersing arrangements or nozzles are designed such that during operation of the reactor, reactants participating in reaction, including gaseous reactants, liquid reactants, powder catalysts, and powder metals, may be uniformly mixed in the reactor for uniform mutual contact by feeding the reactants into the reactor through the nozzles.
Most of such reactions are exothermic. Since the nozzles for mixing/dispersing arrangements establish a rather unstable mixing state in a reactor, it often happens that abnormal exothermic reaction takes place locally, sometimes reaching a temperature above 500.degree. C. For this reason, the nozzles for mixing/dispersing arrangements are conventionally made of heat resisting alloys such as Incoloy.
The nozzles of heat resisting alloys still undergo severe wear during operation of the reactor and cannot withstand the long-term continuous operation thereof because catalyst particles impinge against the nozzles at high velocity during the reactor operation. When the nozzles for mixing/dispersing arrangements are seriously damaged, the reaction itself loses stability to create the risk of explosion. It is thus necessary to replace the mixing/dispersing arrangement nozzles at periodic short intervals before the damage reaches the limit.
Even the use of expensive heat resisting alloy cannot fully suppress the damage to the mixing/dispersing arrangement nozzles. Actually, safe operation is ensured by periodic inspection and premature replacement. These are the bar against production efficiency. The expense for the maintenance and inspection at short intervals and the expense for replacement add to the manufacturing cost.
Therefore, wear resistant, chemical resistant and heat resistant nozzles are desirable as the nozzles for mixing/dispersing arrangements on the floor of a fluidized bed reactor. For example, Japanese Patent Application Kokai (JP-A) No. 180236/1989 discloses that ceramic materials which are obtained by sintering fine powder such as silicon carbide and silicon nitride at high temperature, sometimes at high temperature and high pressure are useful for nozzles for mixing/dispersing arrangements. The mixing/dispersing arrangement nozzles made of these ceramic materials are superior in wear resistance, chemical resistance, corrosion resistance and heat resistance, ensuring stable operation of a fluidized bed reactor for a long time.
Problems arise with these prior art mixing/dispersing arrangement nozzles made of ceramic materials which are obtained by sintering fine powder such as silicon carbide and silicon nitride since sintering of silicon carbide or silicon nitride fine powder is always accompanied by volume shrinkage. In the manufacture of such nozzles of complex configuration requiring dimensional precision, not only a calcined body must be prepared by taking into account the volume shrinkage during sintering, but careful steps must also be taken to prevent deformation during sintering. Even after such a cumbersome process is taken, for nozzles requiring strict dimensional precision, the sintered body must be further machined. Eventually the cost of manufacturing mixing/dispersing arrangement nozzles is increased too much.
It is thus required for the nozzles for mixing/dispersing arrangements on the floor of a fluidized bed reactor that they be not only molded and sintered in a simple manner, but also require as little machining after sintering as possible, to say nothing of the conventional requirements of heat, wear, corrosion and chemical resistance.